Coexpressed Catalase Protects Chimeric Antigen Receptor–Redirected T Cells as well as Bystander Cells from Oxidative Stress–Induced Loss of Antitumor Activity

Abstract

Treatment of cancer patients by adoptive T cell therapy has yielded promising results. In solid tumors, however, T cells encounter a hostile environment, in particular with increased inflammatory activity as a hallmark of the tumor milieu that goes along with abundant reactive oxygen species (ROS) that substantially impair antitumor activity. We present a strategy to render antitumor T cells more resilient toward ROS by coexpressing catalase along with a tumor specific chimeric Ag receptor (CAR) to increase their antioxidative capacity by metabolizing H2O2. In fact, T cells engineered with a bicistronic vector that concurrently expresses catalase, along with the CAR coexpressing catalase (CAR-CAT), performed superior over CAR T cells as they showed increased levels of intracellular catalase and had a reduced oxidative state with less ROS accumulation in both the basal state and upon activation while maintaining their antitumor activity despite high H2O2 levels. Moreover, CAR-CAT T cells exerted a substantial bystander protection of nontransfected immune effector cells as measured by CD3ζ chain expression in bystander T cells even in the presence of high H2O2 concentrations. Bystander NK cells, otherwise ROS sensitive, efficiently eliminate their K562 target cells under H2O2-induced oxidative stress when admixed with CAR-CAT T cells. This approach represents a novel means for protecting tumor-infiltrating cells from tumor-associated oxidative stress–mediated repression.

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…To provide some resistance to the oxidative stress and limit cellular damages due to the exposure to reactive oxygen species (ROS), Ligtenberg et al engineered T cells to express catalase [257]. Tumor encapsulation by extra cellular matrix is considered a potent escape mechanism displayed by certain types of tumor.…”

Programming CAR-T cells to kill cancer

“…Ectopic expression of PPAR-γ co-activator 1α (PCG1α ) can rescue mitochondrial function and lead to increased cytokine production in T cells, resulting in enhanced antitumor efficacy 158 . Modifying cholesterol metabolism by knocking out acyl-CoA:cholesterol acyltransferase 1 (ACAT1), an enzyme involved in esterification of cholesterol, can also potentiate the effector functions of CD8 + T cells 159 , whereas resistance to reactive oxygen species can be conferred by expression of catalase, which relieves oxidative stress in the tumour microenvironment 160 .…”

Incorporation of functional elements enhances the antitumor capacity of CAR T cells

“…Ligtenberg et al [19] presented a strategy to render antitumor T cells more resilient toward ROS by co-expressing catalase along with a tumor-specific CAR to increase their anti-oxidative capacity by metabolizing H 2 O 2 . CAR T cells engineered to co-express catalase (CAR-CAT) showed increased levels of intracellular catalase and sharp decreases in ROS accumulation while maintaining their antitumor activity despite high H 2 O 2 levels.…”